View Compilation Error

0_0_29873592_20220.c: In function 'main':
0_0_29873592_20220.c:10:7: error: 'cin' undeclared (first use in this function)
 while(cin>>n)cout<<((1ll*n*n-1)%mod*inv9)%mod<<endl;
       ^
0_0_29873592_20220.c:10:7: note: each undeclared identifier is reported only once for each function it appears in
0_0_29873592_20220.c:10:14: error: 'cout' undeclared (first use in this function)
 while(cin>>n)cout<<((1ll*n*n-1)%mod*inv9)%mod<<endl;
              ^
0_0_29873592_20220.c:10:48: error: 'endl' undeclared (first use in this function)
 while(cin>>n)cout<<((1ll*n*n-1)%mod*inv9)%mod<<endl;
                                                ^